Thanks for providing the link to Cipher selection UI is messy and irrational
on the PuTTY wishlist.
I think the author of that wish expressed the problem very well. It's unfortunate that no action has been taken since it was logged in 2007...
I really like the WinSCP .Net library and would very much like to use it in the project that I'm currently working on but in order to comply with my customer's security policy I have to ensure that a minimum encryption algorithm of AES 256 is used. So unfortunately I will have to find an alternative library that can meet my needs.
Is there any possibility that in the future you might be able to enhance the the PuTTY code that WinSCP depends on so it is possible to select specific algorithms?